Although solar power generation, wind power generation and the like have such an advantage as to use clean natural energy, they are influenced by a natural condition such as solar radiation or wind state so that it is hard to ensure a stable power generation amount. The unstable power is cannot be exactly transmitted to a power network. For this reason, there is used a technique in which a power generation device is provided with a storage battery and a part of power generation outputs fluctuating at any time depending on a natural condition is charged/discharged to/from a storage battery to stabilize the output and transmit power to a power network.
Moreover, there is also used a technique for charging a part of power obtained by power generation to a storage battery at night (at time of off-peak) that a power demand is small and discharging the power during a daytime (in a peak time period) in which the power demand is great, thereby carrying out peak cut (see Patent Documents 1 and 2, for example).    Patent Document 1: Japanese Laid-Open Patent Publication No. 2009-284586    Patent Document 2: Japanese Laid-Open Patent Publication No. 2004-62254
Referring to Patent Document 1, a difference between a power demand prediction and a purchased power specified value is calculated every time period and is set to be peak power if the demand prediction is greater than the purchased power specified value. The peak power for each time period is integrated to calculate a total amount of the peak power. On the other hand, it is decided whether the total amount of the peak power is larger than the latest charging power amount measured by a charger/discharger or not. If the total amount of the peak power is larger than the latest charging power amount, it is planned to charge power to a storage battery in order to ensure a necessary power storage amount for peak cut before a time period where the peak power is generated. Consequently, the necessary power amount for carrying out the peak cut can be supplied from the storage battery in the time period for the execution of the peak cut.
Referring to Patent Document 2, moreover, a peak-cut position is assumed based on a consumed power pattern which is previously obtained and a rated power generation output of a power generation device is assumed based thereon. A cost reduction effect or an advantage effect is acquired by utilizing a power generation system through a predetermined operation using maximum power of consumed power patterns and a peak-cut position, power rate data, price data of the power generation system, use period data, equipment maintenance, repair cost data and the like.
A value of the rated power generation output which is assumed is changed several times in order to maximize the cost reduction effect or the advantage effect within a range of the assumed peak-cut position. Furthermore, the assumed peak-cut position is changed several times to obtain a rated power generation output and a rated battery capacity which are suitable therefor and to determine a peak-cut position in which the cost reduction effect or the advantage effect is maximized. Thus, it is possible to select the most suitable power generation system for a load to be used by a power consumer or a load for supplying power by a power supplier.
As mentioned above, in Patent Documents 1 and 2, the power demand prediction is performed in advance to obtain the peak-cut amount. In the Patent Document 1, however, the peak-cut amount is obtained based on the difference between the demand prediction and the purchased power specified value. In the Patent Document 2, moreover, the peak-cut amount for the maximization of the cost reduction effect or the advantage effect is acquired based on the consumed power pattern of the demand prediction.
In some cases in which the peak-cut amount is acquired based on the purchased power specified amount in the Patent Document 1 or the cost reduction effect or the advantage effect in the Patent Document 2, however, the peak cut cannot be sufficiently carried out by simple charge/discharge of the storage battery. The peak-cut amount is not acquired in consideration of a free space or a power storage amount of the storage battery which is changed every moment. For this reason, the free space is insufficient so that excessive generated power cannot be sufficiently stored in the storage battery or the power storage amount is insufficient so that the discharge from the storage battery cannot be sufficiently carried out.
In the case in which the charge/discharge of the storage battery cannot cover the execution of the peak cut as described above, a power generator should be controlled to regulate a power generation amount. However, an apparatus accompanied by a rotating machine, for example, a wind power generator has a peculiar difficulty of control and a control delay through inertia which necessarily occur over the rotating machine. For this reason, it is difficult to give a rapid response in peak-cut control for committing a regulation source for a power demand which is changed every moment to the wind power generator of the rotating machine.